Various types of cord locks have been proposed in the past for holding a cord in a tightened or other desired condition in clothing, bags, shoes, and other items. Cord locks provide a convenient alternative to tying knots. Most of these prior cord locks have been formed of two or more parts, adapted to grip and release a cord by relative movement between the parts. The expense involved in forming such parts and then assembling them has limited the use of such locks, and prevented their use in many instances in which it might otherwise be desirable to utilize a lock in lieu of hand tying a cord.
Other cord locks have made use of elastomeric materials, those materials with elastic properties resembling those of natural rubber, in order to provide less expensive single-piece devices. U.S. Pat. No. 5,440,788 to Boden, which is incorporated by reference in its entirety into the present disclosure, discloses a cord lock with a single slit extending through an elastomeric body. The natural resilience of the elastomeric material holds the cords in place by forcing the walls of the body against the cords. The cords are released by squeezing on the sides of the elastomeric body. U.S. Pat. No. 5,182,838 to Stenner shows a similar cord locking device also utilizing a single slit extending though the cord lock's elastomeric body. There are several disadvantages to these prior art cord locks. First, with the prior art designs, a major inconvenience is caused by the cords pulling out from the cord lock causing the cord lock to fall off from the cord. The cords must be repeatedly rethreaded through the cord lock. Even when the ends of the cords are tied into knots, the single slit is large enough to allow the cords to slip out from the cord lock, knot and all. This problem is particularly serious when using the cord lock with infants and toddlers who often pull the cord lock off of the cords, leading to the risk of the child swallowing and choking on the cord lock.
Further, the prior art cord locks provide the same amount of locking force whether it is needed or not, rather than providing more locking force when more is required. They also use a continuous, large locking force. This large locking force is dangerous for infants and toddlers because they could put a cord fastened with such a cord lock around their necks and accidentally strangle themselves due to the relatively strong locking force preventing them from loosening the cord once it is tightened.
U.S. Pat. No. 1,907,629 to Walty discloses a soft rubber lace fastener utilizing a single opening. This invention also has the disadvantage of the cords slipping out from the cord lock and has the further disadvantage that, even when using the lace fastener, a single knot still must be tied. This invention merely keeps an existing knot from coming undone rather than eliminating the need for a knot altogether.
U.S. Pat. No. 3,043,902 to Klein discloses aplastic device for spacing a double wire transmission line. This device utilizes open slits which would allow a cord to slip out from its openings.